What size bike for 5'8" (173 cm)?
The most common height on the size boundary. Here's how to land on the right side of it.
Short answer: at 5'8" you usually land on a medium: roughly a 52 to 56 cm road frame depending on the brand, and a medium (sometimes ML) mountain bike.[1 2 2nd-hand 3 2nd-hand · Oct 29, 2026; 4 2nd-hand · Oct 28, 2026] 5'8" sits right on a size boundary in several brand charts, so check the chart for the exact bike and your inseam.
Road bikes at 5'8"
| Chart | Size at 173 cm | Range that size covers |
|---|---|---|
| General guide[1 · Oct 29, 2026] | M (54–55 cm effective top tube) | 168–175 cm |
| Specialized Tarmac / Aethos / Allez[2 2nd-hand · Oct 29, 2026] | 54 or 56 | 54: 165–173 cm; 56: 173–180 cm |
| Merida Reacto / Scultura[3 2nd-hand · Oct 29, 2026] | S/M (52) or M/L (54) | 52: 168–175 cm; 54: 173–183 cm |
Mountain bikes at 5'8"
| Chart | Size at 173 cm | Range that size covers |
|---|---|---|
| Trek Marlin (Gen 3)[4 2nd-hand · Oct 28, 2026] | M or ML | M: 165–177 cm, 31–33 in inseam; ML: 173–180 cm, 32–34 in inseam |
| Specialized XC / hardtail[5 2nd-hand · Oct 28, 2026] | M | 165–178 cm |
| Specialized S-Sizing (trail)[6 · Oct 28, 2026] | S3 (balanced); S2 nimbler, S4 more stable | S3: 5'5"–5'11" |
Tables are our own restatement of each published chart, read at 173 cm. Brand letter and cm sizes do not line up across brands, so go by height and inseam, not the label.
Between two sizes?
- Check your inseam. Long legs for your height point to the larger size; short legs to the smaller. Trek's Marlin chart lists inseam ranges for each size.[4 2nd-hand · Oct 28, 2026]
- Riding style: Specialized describes the smaller size as more nimble and the larger as more stable at speed.[6 · Oct 28, 2026]
- Compare reach and stack (or effective top tube) on the geometry chart of the two sizes, not just the size label.[1 · Oct 29, 2026]
- Test ride both sizes at a shop if you can.
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More heights: road bike size chart and mountain bike size chart.
Sources: 1. BikeRadar, Road bike sizing (re-checked Oct 29, 2026). 2. Specialized road size guides as published by UK dealer Cyclestore (second-hand; re-checked Oct 29, 2026). 3. Merida size guide as published by UK dealer Tredz (second-hand; re-checked Oct 29, 2026). 4. Trek's Marlin Gen 3 sizing table as published by Trek dealer The Wheel House (second-hand). 5. Specialized size guides as published by UK dealer The Ark Cycles (second-hand). 6. Specialized, S-Sizing. Checked Oct 28, 2026. Trademarks belong to their owners; charts are restated, not reproduced.